Recent improvements in their spatial and data resolution capability have made digital image processing systems particularly attractive for multi-use environments, in which the user has the option of selecting the type of reproduction device and the desired resolution of the reproduction device. In still color image photography, for example, when an image, that has been captured on color photographic film or a high spatial resolution color digital camera, is digitized and stored in an attendant data base, it can be readily optimized for reproduction on a variety of output devices (e.g. a color video display or a digitally driven, high resolution color thermal printer) through the use of workstation-resident image processing software. In the case of a constant reproduction device, it may be desirable to uniquely modify portions of an image or the total image for desired reproduction in manner that is different than the manner used for other images.
One example of a digitized image processing system that takes advantage of this capability is the color photo-finishing system described in co-pending patent application Ser. No. 582,305, filed Sep. 14, 1990, by S. Kristy entitled "Multi-Resolution Digital Imagery Photofinishing System," assigned to the assignee of the present application and the disclosure of which is herein incorporated. As explained in that application, conventional photo-finishing of consumer-generated still color photographs (e.g. those captured on 35mm color film) customarily involves the use of an analog electro-optic system and an associated chemical-based print developing unit. The Kristy application describes a digital image-based photofinishing apparatus that enables the user to personally customize and obtain high quality prints of photographic images. It also provides for the storage and retrieval of high spatial resolution digitized color still images for playback to a variety of reproduction devices, the spatial resolution of which may vary.
FIG. 1 diagrammatically illustrates such an improved photofinishing apparatus as employing a high spatial resolution film scanner 32 that is used to scan an image, for example, from film strip 36. The high spatial resolution scanner 32 has built therein means for converting the scanned image into corresponding digital signals representing a pixel array that may be processed in various ways by a host computer 34. The term high spatial resolution, as applied to a pixel array from a scanner, means, a pixel array of a size and a population that is sufficient to provide a color print having a quality equal to that normally provided by analog optical systems. The host computer 34 is interfaced to monitor 39 and associated keyboard (not shown) for permitting an operator to interface with the control functions and operating programs of the host computer. The output images from the host computer 34 can be directed to a high resolution printer 38 and/or to a TV display 37. The TV display 37, with present technology, would not be able to display as finely a detailed image as is obtained on a photographic print.
The digital image signals supplied to the host computer 34 are in the form of an imaging pixel array-representative bit map, resolved to a prescribed digital code width (e.g. eight bits per color per pixel). Host computer 34 has a resident image-encoding and storage operator through which each high spatial resolution digitized image file may be stored in a multi-resolution, hierarchical format.
One example of a preferred encoding and storage operator that may be used for this purpose is described in U.S. Pat. No. 4,969,204, entitled "A Hybrid Residual-Based Hierarchical Storage and Display Method for High Resolution Digital Images in a Multi-Use Environment," by Paul W. Melnychuck et al, which patent is assigned to the assignee of the present application and the disclosure of which is herein incorporated.
To optimize the performance of aforementioned reproduction systems in different conditions it is often necessary that modifications be made in the transform. The modification may involve anything from a single-channel independent modification to the use of a series of multi-channel color space transformations. Although a low level transform modification may not require a significant amount of additional image processing, executing a more intense transform modification in a very high spatial resolution application, such as would be needed for a 2040.times.3072 pixel array printer, can be particularly computationally intense.
Although the system described in U.S. patent application Ser. No. 631,709, affords rapid access to a variety of image formats and allows the user to select the reproduction medium and spatial resolution at which the accessed image is reproduced, there still remains the problem of transforming the digitized image file in the event that a change in metric, for example, a change in color metric to accommodate a particular display option (device and/or desired color reproduction), is desired.
Based on the above, it would be advantageous to have a simplified method and apparatus for achieving high quality metric conversion (for multiple display options and/or image processing, such as color enhancement options) with less computational burden by capitalizing on the hierarchical structure and the nature of the stored (or starting) metric image that easily allows for simplified transformation of high frequency image information.